[Beignet] OpenCV Morph OCL Perf case is crash based on beignet

[yan.wang at linux.intel.com]

Hi, All,
  Today I tried the latest opencv code (3.0 master) and found morph perf
case will crash when test CV_8UC1 type only.
  The case number is the following:
  opencv_perf_imgproc
--gtest_filter=OCL_MorphologyExFixture_MorphologyEx.MorphologyEx/4.
  Its operation type is MORPHY_GRADIENT.
  I do the initial debug and found it crashed in llvm_legalize.cpp line
516 because insn->getOpcode() couldn't get a valid op code.

  %.0.i = phi i128 [ %phitmp962, %58 ], [ 0,
%isBorder.exit.thread.thread650 ], [ 0, %19 ], [ 0, %25 ]
ASSERTION FAILED: false && "Illegal instruction\n"
  at file /home/yanwang/beignet/backend/src/llvm/llvm_legalize.cpp,
function bool gbe::Legalize::legalizeFunction(llvm::Function&), line 516

  After asked Junyan, it seems "phi" op code hasn't been supported.
  Thanks.

Yan Wang